Abrasive water jet cutting machine

ABSTRACT

To provide an abrasive water jet cutting machine in which an abrasive recovery unit can be continuously used without needing maintenance, and an abrasive having a uniform grain size can be easily recovered, the machine has a catch tank for receiving a high-pressure abrasive mixture liquid jetted from a jet nozzle, and an abrasive recovery unit that recovers abrasive having a grain size in a reusable predetermined range from the abrasive mixture liquid transported from the catch tank, and transports abrasive mixture liquid including recovered abrasive into an abrasive-mixture-liquid retention tank; wherein the abrasive recovery unit has an abrasive sorting tank which flows the abrasive mixture liquid transported from the catch tank in an approximately horizontal direction, and sorts abrasive depending on grain size by using difference in sedimentation rate depending on grain size, and recovers the abrasive having the grain size in the reusable predetermined range.

BACKGROUND OF THE INVENTION

1. Field of the Invention

The present invention relates to an abrasive water jet cutting machine for cutting workpiece by jetting a high-pressure liquid including abrasive.

2. Related Art

A water jet is a jet stream of high-pressure water formed by providing energy to water by a super high-pressure pump and the like, and for example, has flow velocity one to three times faster than the sound velocity. In these years, methods and machines for cutting various kinds of workpiece by using the water jet have been developed. In particular, an abrasive jet is now noticed in order to improve a cutting efficiency, in which solid abrasive is mixed in high-pressure water. The abrasive includes a material having high hardness such as gamet, alumina, and silicon carbide, which has a granular body having a grain size of, for example, about several ten to several hundred micrometers. The abrasive collides with the workpiece at high speed with the high-pressure water so that the workpiece is cut while being partially broken.

Such cutting by the water jet has an advantage that the workpiece can be cut without any thermal effect, and occurrence of burrs in a cutting surface can be reduced by the abrasive. Furthermore, the cutting has another advantage that even if a cutting line is a curved line, the workpiece can be cut without any difficulty, in addition, it is suitable for cutting a composite material or a material of hard workability. Therefore, in these years, a cutting process using the water jet has been investigated for dicing of a semiconductor substrate, in particular, a packaged substrate, instead of using a dicing blade as usual.

In the so-called abrasive water jet cutting machine using the abrasive jet, the abrasive that was used for the cutting process is generally recovered for reuse (for example, JP-A-10-66895 and JP-A-2001-79443). This is because all abrasive jetted with the high-pressure water from a jet nozzle is not consumed to contribute to the process in one time of cutting of the workpiece, therefore if the abrasive is disposable, a large amount of unconsumed abrasive is disposed, consequently production efficiency is significantly reduced.

Thus, the inventors of the application have investigated an abrasive water jet cutting machine so far, in which abrasive is automatically circulated to be reusable by using abrasive recovery apparatus 160 having an abrasive recovery filter 167, as shown in FIG. 4. In the abrasive water jet cutting machine, as shown in FIG. 4, abrasive mixture liquid in an abrasive-mixture-liquid retention tank 122 a or 122 b is fed out at high pressure by high-pressure water supplied from a high-pressure pump 115, and the high-pressure abrasive mixture liquid (abrasive jet) J is jetted from a jet nozzle 130 to workpiece 105 for cutting. Furthermore, the abrasive mixture liquid J jetted from the jet nozzle 130 is received by a catch tank 150, and then abrasive having a reusable grain size (for example, 25 to 100 μm) is recovered from the relevant abrasive mixture liquid by the abrasive recovery apparatus 160, and replenished into one of the abrasive-mixture-liquid retention tanks 122 a and 122 b, which is not being used for the cutting process.

In the abrasive recovery apparatus 160, the abrasive recovery filter 167 that was able to transmit grains having a predetermined size or less (for example, 100 μm or less) was used, and the abrasive mixture liquid was designed to be flown at a certain flow velocity (for example, 8 liter/min using a positive-pressure pump) on the abrasive recovery filter 167 with the abrasive recovery filter 167 being oscillated, and thus an abrasive having a grain size in a predetermined range (for example, 25 to 100 μm) passed through the abrasive recovery filter 167 was sorted and recovered. This is because abrasive having excessively small grain size can not contribute to polishing even if it is reused, and on the other hand, abrasive having excessively large grain size may cause dogging of the jet nozzle 130.

However, in the abrasive recovery apparatus 160 as shown in FIG. 4, since the abrasive recovery filter 167 is used, meshes of the abrasive recovery filter 167 may be dogged by the abrasive. Therefore, a measure was taken, in which the abrasive recovery filter 167 was regularly cleaned so that the abrasive was separated from the meshes to eliminate the dogging, however, since the meshes are worn by the abrasive, the abrasive recovery filter 167 needs to be replaced with a new filter.

However, in the abrasive recovery apparatus 160, there has been a difficulty that since the abrasive recovery filter 167 is disposed in a firmly sealed housing, it is extremely difficult for an operator to replace the abrasive recovery filter 167.

Moreover, in the abrasive recovery apparatus 160, an abrasive having an extremely small grain size is washed away by a water stream without passing through the abrasive recovery filter 167 because of its light weight, and an abrasive having an extremely large grain size is also washed away by the water stream and discharged because it can not pass through the abrasive recovery filter 167. However, as a result of verification of the inventors of the application, it was found that abrasive (for example, in a size of 25 to 100 μm) to be essentially recovered by the abrasive recovery apparatus 160 was mixed in the abrasive to be discharged. It is considered to be one reason for this that since a minimum of the grain size is controlled by flow velocity of the water stream, the minimum is extremely unstable. There has been a further difficulty that the amount of the abrasive that is discharged in this way despite being reusable is estimated to reach about 8% of the total amount of reusable abrasive, thereby productivity is significantly reduced.

Furthermore, since the grinding force of the abrasive jet is determined by the grain size of the abrasive, the abrasive is desirably made to have uniform grain size to the utmost in order to realize stable quality. However, if the quality is intended to be realized in the abrasive recovery apparatus 160, it is necessary that the flow velocity of the abrasive mixture liquid flowing on the abrasive recovery filter 167 is increased, and the meshes of the abrasive recovery filter are reduced, consequently a ratio of the reusable abrasive that can not be recovered is further increased, therefore it is extremely difficult to make the grain size of the abrasive uniform.

SUMMARY OF THE INVENTION

It is an object to provide a new and improved abrasive water jet cutting machine, in which an abrasive recovery unit can be continuously used without needing maintenance, and an abrasive having uniform grain size can be easily recovered.

To overcome the difficulties, an abrasive water jet cutting machine according to the present invention including an abrasive-mixture-liquid retention tank for retaining an abrasive mixture liquid in which an abrasive and a liquid are mixed, a high-pressure liquid supply unit for feeding out the abrasive mixture liquid retained in the abrasive-mixture-liquid retention tank at high pressure by supplying a high-pressure liquid to the abrasive-mixture-liquid retention tank, a jet nozzle for jetting the high-pressure abrasive mixture liquid, which is fed out from the abrasive-mixture-liquid retention tank, to workpiece, a catch tank for receiving the high-pressure abrasive mixture liquid jetted from the jet nozzle, and an abrasive recovery unit that recovers abrasive having grain size in a reusable predetermined range from the abrasive mixture liquid transported from the catch tank, and transports abrasive mixture liquid including recovered abrasive into the abrasive-mixture-liquid retention tank, thereby cutting the workpiece by the high-pressure abrasive mixture liquid jetted from the jet nozzle; wherein the abrasive recovery unit has an abrasive sorting tank that flows the abrasive mixture liquid transported from the catch tank in an approximately horizontal direction, and sorts abrasive depending on grain size of the abrasive by using difference in sedimentation rate caused by grain size of the abrasive, and recover the reusable abrasive having the grain size in the predetermined range; the abrasive sorting tank has a flow inlet provided on an upper portion at one end side, a flow outlet provided on an upper portion at the other end side, a first sorting member as a partition member that is set at a side of the flow inlet in a bottom and divides the bottom, a second sorting member as a partition member that is set at a side of the flow outlet in the bottom and divides the bottom, and a first discharge port set between the first and second sorting members; and when the abrasive mixture liquid transported from the catch tank flows in the approximately horizontal direction from the flow inlet to the flow outlet, the abrasive sorting tank sediments abrasive having a grain size larger than a maximum of the reusable predetermined range included in the relevant abrasive mixture liquid in a side near the flow inlet side compared with the first sorting member, sediments abrasive having a grain size in the reusable predetermined range between the first and second sorting members, and sediments abrasive having a grain size smaller than a minimum of the reusable predetermined range in a side near the flow outlet side compared with the second sorting member, and discharges the abrasive having the grain size in the reusable predetermined range from the first discharge port and recover it.

According to such an abrasive sorting tank, the abrasive having the grain size in the reusable predetermined range can be sorted and recovered without using the abrasive recovery filter. Therefore, the abrasive recovery unit can be continuously used over a long period without needing maintenance of the abrasive recovery unit. Moreover, according to the abrasive sorting tank, since the abrasive is accurately sorted and thus uniform abrasive is easily obtained compared with a case of using the abrasive recovery filter, cutting quality of workpiece can be improved.

Height of each of the first and second sorting members may be changed. Thus, height of the first sorting member is changed, thereby maximal grain size of the abrasive to be recovered for reuse can be changed, and height of the second sorting member is changed, thereby minimal grain size of the abrasive to be recovered for reuse can be changed.

The abrasive sorting tank may further have a second discharge port set at a side near the flow inlet compared with the first sorting member in the bottom, and a third discharge port set at a side near the flow outlet compared with the second sorting member in the bottom, in order to discharge the abrasive having the grain size larger than the maximum of the reusable predetermined range from the second discharge port, and discharge the abrasive having the grain size smaller than the minimum of the reusable predetermined range from the third discharge port. Thus, the abrasive having a large grain size in a level of dogging a drain ditch can be sorted and recovered to be disposed or used for other applications.

As described hereinbefore, according to the present invention, since the abrasive recovery filter is not used, the abrasive recovery unit can be continuously used over a long period without needing maintenance of the abrasive recovery unit. Moreover, since the uniform abrasive is easily obtained compared with the case of using the abrasive recovery filter, cutting quality of workpiece can be improved.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a schematic view showing a general configuration of a water jet cutting machine according to a first embodiment of the invention;

FIG. 2A is a perspective view showing an outside configuration of an abrasive sorting tank according to the embodiment;

FIG. 2B is a perspective view showing an internal configuration of the abrasive sorting tank according to the embodiment;

FIG. 3 is a vertical section view showing an internal configuration of the abrasive sorting tank according to the embodiment; and

FIG. 4 is an explanatory view showing a general configuration of a water jet cutting machine in the related art.

DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENTS

Hereinafter, a preferred embodiment of the invention will be described in detail with reference to accompanying drawings. In this specification and the drawings, components having substantially the same functions and configurations are marked with the same signs, so that overlapped description is omitted.

First Embodiment

Hereinafter, an abrasive water jet cutting machine according to a first embodiment of the invention is described. While the abrasive water jet cutting machine according to the embodiment is configured as, for example, a water jet cutting machine for cutting workpiece by a jet stream of high-pressure water mixed with the abrasive (abrasive jet) as described below, the invention is not limited to such an example.

First, a general configuration of a water jet cutting machine 1 according to the embodiment is described according to FIG. 1. FIG. 1 is an explanatory view showing a general configuration of the water jet cutting machine 1 according to the embodiment.

As shown in FIG. 1, the water jet cutting machine 1 according to the embodiment is a cutting machine that can perform an accurate cutting process (that is, water jet process) to workpiece 5 at a comparatively free cutting line by jetting high-pressure water including abrasive. While the workpiece 5 as a cutting object of the water jet cutting machine 1 includes various semiconductor substrates such as a silicon wafer and a packaged semiconductor substrate (for example, CSP substrate), it is not limited to such examples.

For example, such a water jet cutting machine 1 mainly has a high-pressure supply unit 10 including a high-pressure pump 15, an abrasive mixing unit 20 including abrasive-mixture-liquid retention tanks 22 a, 22 b, a jet nozzle 30 for jetting a water jet J, a holding table 40 for holding the workpiece 5, a table transfer unit (not shown) for transferring the holding table, a catch tank 50 for receiving the water jet J, and an abrasive recovery unit 60 having a sorting tank 70 and a recovered abrasive retention tank 80. Hereinafter, respective components configuring such a water jet cutting machine 1 are described in detail.

The high-pressure pump 15 configuring the high-pressure supply unit 10 pressurizes water supplied from the outside, thereby generates high-pressure water of, for example, 600 to 700 bars (1 bar is about 1.02 kgf/cm²) to be supplied. The water supplied from the outside is, for example, tap water, however, it is not limited to such an example, and may be pure water and the like. The high-pressure water produced by the high-pressure pump 15 is supplied to the abrasive-mixture-liquid retention tanks 22 a, 22 b of the abrasive mixing unit 20 via a pipeline 12 for supplying the high-pressure liquid.

The abrasive mixing unit 20 includes the two abrasive-mixture-liquid retention tanks 22 a, 22 b (hereinafter, they may be collectively called “abrasive-mixture-liquid retention tank 22”) for retaining the abrasive mixture liquid in which abrasive (abrasive grains) and water are mixed, the confluence 23, and a plurality of pipe lines and valves for connecting them. The abrasive includes a material having high hardness such as gamet, alumina, silicon carbide, and diamond, which is in a granular body having a grain size of, for example, about several ten to several hundred micrometers, and functions to improve cutting efficiency of the high-pressure water. In the embodiment, alumina having a grain size of, for example, 40 to 100 μm is used as the abrasive.

Such an abrasive mixing unit 20 pushes out abrasive mixture water retained in one abrasive-mixture-liquid retention tank 22 a at high pressure by pressure of the high-pressure water supplied from the high-pressure pump 15, and sent out the high-pressure abrasive mixture water to the jet nozzle 30 via a pipe line 21. At that time, the other abrasive-mixture-liquid retention tank 22 b is replenished with abrasive recovered by the abrasive recovery unit 60 via a pipeline 61 and retains the relevant abrasive, and sent out unnecessary water to the abrasive recovery unit 60 via a pipeline 63.

When the retaining amount of abrasive in the one abrasive-mixture-liquid retention tank 22 a being used for the cutting process is decreased to a predetermined level or less, operation of the abrasive-mixture-liquid retention tank 22 a is changed with that of the abrasive-mixture-liquid retention tank 22 b, so that in the same way as above, the abrasive mixture water is supplied to the jet nozzle 30, and concurrently with this, the abrasive is replenished from the abrasive recovery unit 60. Thus, the high-pressure abrasive mixture water can be supplied to the jet nozzle 30 stably and continuously. It is also acceptable that at least three abrasive-mixture-liquid retention tanks 22 are provided and used while being switched from one another.

The jet nozzle 30 jets the high-pressure abrasive mixture water supplied from the abrasive mixing unit 20 to the workpiece 5 held by the holding table 40 from above as the water jet J. Thus, the workpiece 5 can be cut by energy of the high-pressure water. At that time, since the abrasive collides with the workpiece 5 with the high-pressure water so that the workpiece is cut with being partially broken, cutting efficiency can be improved. In this way, the water jet J according to the embodiment is configured as an abrasive jet.

The table transfer unit (not shown) transfers the holding table 40 as a workpiece holding unit in a horizontal direction (X and Y axis directions) and a vertical direction (Z axis direction). Thus, the holding table 40 is transferred in the X and Y axis directions relatively to the relevant jet nozzle 30 while jetting the water jet J from the jet nozzle 30, thereby the water jet J including the abrasive is allowed to work along an expected cutting line of the workpiece 5, consequently the workpiece 5 can be continuously subjected to the cutting process.

The catch tank 50 is, for example, a vertical-long water storage tank having an opened top, and acts as a receiver tank of the water jet J. That is, the catch tank 50 can receive the water jet J, which has penetrated through the workpiece 5 after cutting it in the above way, with power of the water jet J being reduced by retained water as a buffer. On a bottom of the catch tank 50, the abrasive included in the water jet J received in the above way is sedimented and deposited. The abrasive mixture water including the abrasive deposited on the bottom of the catch tank 50 is transported to the abrasive recovery unit 60 by a first positive-pressure pump 59 via a pipeline 51.

The abrasive recovery unit 60 is abrasive recovery apparatus in a sedimentation type unlike the abrasive recovery apparatus 160 in an abrasive recovery filter type in the related art. The abrasive recovery unit 60 has the abrasive sorting tank 70 and the recovered abrasive retention tank 80.

The abrasive sorting tank 70 sorts and recovers abrasive having a grain size in a reusable predetermined range, that is, a grain size of a predetermined minimum (for example, 25 μm) or more and a grain size of a predetermined maximum (for example, 100 μm) or less from the abrasive mixture liquid transported from the catch tank 50, and transports the abrasive mixture water including the recovered abrasive to the recovered abrasive retention tank 80 via a pipeline 66. Moreover, the abrasive sorting tank 70 sorts and recovers abrasive having a grain size larger than the maximum, and sends out it to an abrasive recovery filter 101 via a pipe line 64. Furthermore, the abrasive sorting tank 70 sorts and recovers abrasive having a grain size smaller than the minimum, and sends out it to an abrasive recovery filter 102 via a pipe line 65. Abrasive mixture water including abrasive that has not been recovered by the abrasive sorting tank 70 is discharged to the outside by a third positive-pressure pump 79 via a pipeline 62. Such an abrasive sorting tank 70 is a unique configuration according to the embodiment, and described later in detail.

The recovered abrasive retention tank 80 retains the abrasive mixture water including the reusable abrasive recovered by the abrasive sorting tank 70. The abrasive mixture water including abrasive deposited on a bottom of the abrasive retention container 80 is transported to the abrasive mixture liquid retention tank that is not being used for the cutting process in the two abrasive mixture liquid retention tanks 22 a, 22 b by the second positive-pressure pump 69 via the pipeline 61.

The water jet cutting machine 1 in a configuration as above sends out the abrasive mixture water in the abrasive mixture liquid retention tank 22 a or 22 b at high pressure by the high-pressure water supplied from the high-pressure pump 15, and jets the high-pressure abrasive mixture water (abrasive jet) from the jet nozzle 30 to the workpiece 5 for the cutting process. Furthermore, the machine is in a configuration where the catch tank 50 receives the abrasive mixture water jetted from the jet nozzle 30, and then the abrasive recovery unit 60 recovers the abrasive, which is not wasted and has a reusable grain size (for example, 25 to 100 μm), from the relevant abrasive mixture water, and returns the abrasive to the tank that is not being used for the cutting process in the two abrasive mixture liquid retention tanks 22 a, 22 b. According to such a configuration, the abrasive can be automatically circulated within the water jet cutting machine 1 and efficiently reused.

Next, the abrasive sorting tank 70 as a feature according to the embodiment is described in detail according to FIGS. 2A to 2B and FIG. 3. FIG. 2A is a perspective view showing an outside configuration of the abrasive sorting tank 70 according to the embodiment, FIG. 2B is a perspective view showing an internal configuration of the abrasive sorting tank 70 according to the embodiment, and FIG. 3 is a vertical section view showing an internal configuration of the abrasive sorting tank 70 according to the embodiment.

As shown in FIGS. 2A to 2B and FIG. 3, the abrasive sorting tank 70 functions to flow the abrasive mixture water transported from the catch tank 50 in an approximately horizontal direction near a liquid level W, and sort the abrasive in the relevant abrasive mixture water by using difference in sedimentation rate of the abrasive depending on grain size, and recover the abrasive having the grain size in the reusable predetermined range.

The abrasive sorting tank 70 has a housing 71 in an approximately rectangular prism shape for retaining the abrasive mixture water, a buffer tank 72 being set in an upper portion in one side of the housing 71 and connected with the pipe line 51 from the catch tank 50, a flow inlet 91 provided in a lower outlet of the buffer tank 72, a flow outlet 92 set in an upper portion in the other side of the housing 71, a first sorting member 73 set at a flow inlet 91 side in a bottom of the housing 71, a second sorting member 74 set at a flow outlet 92 side in the bottom of the housing 71, a liquid-level measuring sensor 75 for measuring height of the liquid level W of the abrasive mixture water retained in the housing 71, a connection member 76 for connecting between the bottom of the housing 71 and the pipeline 66, a first discharge port 94 set between the first sorting member 73 and the second sorting member 74 in the bottom of the housing 71, a second discharge port 93 set at a side near the flow inlet port 91 compared with the first sorting member 73 in the bottom of the housing 71, and a third discharge port 95 set at a side near the flow outlet port 92 compared with the second sorting member in the bottom of the housing 71.

As shown in the figures, the abrasive sorting tank 70 is a water tank that can retain the abrasive mixture water within the housing 71 in the approximately rectangular prism shape. In the upper portion of the housing 71, the flow inlet port 91 and the flow outlet port 92 for the relevant abrasive mixture water are set in places where the abrasive mixture water transported from the catch tank 50 is flown in a horizontal direction within the housing 71. The flow inlet port 91 and the flow outlet port 92 are set at approximately the same height in the housing 71, and positioned in a side lower than the retained liquid level W at the maximum.

On the upper portion of the housing 71 at a side where the flow inlet 91 is positioned, the buffer tank 72 is provided, which temporarily retains the abrasive mixture water transported from the catch tank 50. Since a fixed amount of abrasive mixture water is not always transported from the catch tank 50 to the abrasive sorting tank 70, the buffer tank 72 temporarily retains the abrasive mixture water such that a fixed amount of abrasive mixture water is always flown from the flow inlet 91 positioned in the lower portion of the buffer tank 72 into the housing 71.

Furthermore, in the lower outlet of the buffer tank 72, a regulation member 721 is set, the member being formed by a sheet member having an L-shaped section. At one side of the regulation member 721, the flow inlet 91 is formed in a manner of opening in a lateral direction. Such a regulation member 721 regulates the abrasive mixture water discharged from the bottom of the buffer tank 72 such that it does not flow out in a vertically downward direction, and guides the water to flow out in a horizontal direction from the flow inlet 91. Thus, a horizontal stream of the abrasive mixture water can be preferably generated in the upper portion within the housing 71.

Moreover, the liquid-level measuring sensor 75 is provided in the upper portion of the housing 71, which is for measuring the height of the liquid level W of the abrasive mixture water retained in the abrasive sorting tank 70. The liquid-level measuring sensor 75 is configured by, for example, a small capacitance-type liquid level sensor, and measures the height of the liquid level W according to difference in capacitor (capacitance) between an electrode and an inner wall of a container. According to a measurement result by such a liquid-level measuring sensor 75, a flow rate of the abrasive mixture water outputting/inputting from/into the abrasive sorting tank 70 is controlled, thereby the height of the liquid level W is adjusted. Specifically, the height of the liquid level W is adjusted such that the liquid level W is higher than each position of the flow inlet 91 and the flow outlet 92, and it does not reach the ceiling of the housing 71.

According to the above configuration, the abrasive mixture water transported from the catch tank 50 to the abrasive sorting tank 70 via the pipe line 51 can be temporarily retained in the buffer tank 72, then flown from the flow inlet 91 into the housing 71, and flown in the horizontal direction in the upper portion within the housing 71, and in turn discharged to the outside from the flow outlet 92 via the pipe line 62.

Next, in the abrasive sorting tank 70, a configuration for sorting abrasive depending on grain size is described, the abrasive being included in the abrasive mixture water flowing in the horizontal direction.

On the bottom of the housing 71, the first sorting member 73 is disposed at a side near the flow inlet port 91, and the second sorting member 74 is disposed at a side near the flow outlet port 92. Each of the first and second sorting members 73 and 74 is configured by, for example, a triangular prism unit, and disposed in a manner of dividing the bottom of the housing 71 in a perpendicular direction to the direction of the horizontal flow.

The first sorting member 73 is configured by, for example, a comparatively large triangular-prism-unit, and disposed with an inclined surface 73 a being at a side of the flow outlet 92 and a vertical surface 73 b being at a side of the flow inlet 91. The first sorting member 73 acts as a partition member for sorting size of the maximal grain size (for example, 100 μm) of reusable abrasive. Height h1 of such a first sorting member 73 is changed, thereby the size of the maximal grain size of the abrasive to be recovered for reuse can be changed. In this case, several kinds of triangular-prism-units having different height h1 may be prepared as the first sorting member 73 such that the relevant triangular-prism-unit is selectively disposed depending on set maximal grain size, or the first sorting member 73 may be configured such that the height h1 of the member itself can be changed depending on the set maximal grain size.

The second sorting member 74 is configured by a small triangular-prism-unit compared with the first sorting member 73, and disposed with an inclined surface 74 a being at a side of the flow inlet 91 and a vertical surface 74 b being at a side of the flow outlet 92. The second sorting member 74 acts as a partition member for sorting size of the minimal grain size (for example, 25 μm) of the reusable abrasive. Height h2 of such a second sorting member 74 is changed, thereby the size of the minimal grain size of the abrasive to be recovered for reuse can be changed, as the first sorting member 73.

The first and second sorting members 73 and 74 as above are disposed, thereby the bottom of the housing 71 is divided into three bottom areas along the direction of the horizontal flow. In the three bottom areas, a bottom area (left area in FIG. 3) at a side near the flow inlet 91 compared with the first sorting member 73 is an area where abrasive having a grain size larger than the maximal grain size of the reusable abrasive (for example, larger than 100 μm) is sedimented and deposited. A bottom area between the first and the second sorting members 73 and 74 (central area in FIG. 3) is an area where abrasive having a grain size in the reusable predetermined range (for example, 25 μm to 100 μm) is sedimented and deposited. A bottom area (right area in FIG. 3) at a side near the flow outlet 92 compared with the second sorting member 74 is an area where abrasive having a grain size smaller than the minimal grain size of the reusable abrasive (for example, smaller than 25 μm) is sedimented and deposited.

According to a configuration as above, by using difference in sedimentation rate of abrasive depending on grain size, abrasive included in the abrasive mixture water horizontally flowing in the housing 71 is sorted, so that the abrasive having the grain size in the reusable predetermined range can be recovered.

Specifically, the inputted abrasive mixture water from the flow inlet 91 is horizontally flown in the upper portion within the housing 71, and then discharged to the outside from the flow outlet 92. At that time, abrasive having a fine grain size (for example, 10 μm or less) is discharged to the outside from the flow outlet 92 with the horizontal flow without sedimenting in the abrasive sorting tank 70 (refer to an arrow A in FIG. 3). Such abrasive having the fine grain size does not dog the discharge ditch even if it is discharged as it is.

Since the abrasive having the grain size larger than the maximal grain size of the reusable abrasive, which is included in the horizontally flowing abrasive mixture liquid, has large sedimentation rate, it sediments in the bottom area at the side near the flow inlet 91 compared with the first sorting member 73 (refer to an arrow B in FIG. 3). Since the abrasive having the grain size in the reusable predetermined range has medium segmentation rate, it sediments in the bottom area between the first and second sorting members 73 and 74 (refer to an arrow C in FIG. 3). Furthermore, the abrasive having the grain size smaller than the minimal grain size of the reusable abrasive has small segmentation rate, it sediments in the bottom area at the side near the flow outlet 92 compared with the second sorting member 74 (refer to an arrow D in FIG. 3).

In this way, the abrasive sorting tank 70 sorts the abrasive by using difference in sedimentation rate of abrasive depending on grain size, so that the abrasive can be deposited in each of the three bottom areas divided by the first and second sorting members 73 and 74. Thus, for example, when the minimal grain size of the reusable abrasive is set to be 25 μm, and the maximal grain size is set to be 100 μm, abrasive having a grain size larger than 100 μm can be excluded from a recovery object by the first sorting member 73, and abrasive having a grain size smaller than 25 μm can be excluded from the recovery object by the second sorting member 74.

That is, in the bottom area between the first and second sorting members 73 and 74, the abrasive having the reusable predetermined grain size (for example, 25 μm to 100 μm) is sedimented and deposited. Such abrasive having the reusable grain size is sent out from the first discharge port 94 provided in the relevant bottom area to the recovered abrasive retention tank 80 via the pipeline 66 and retained therein (refer to FIG. 1). The abrasive retained in the recovered abrasive retention tank 80 is timely transported to the abrasive-mixture-liquid supply tank 22 for reuse.

In the bottom area at the side near the flow inlet 93 compared with the first sorting member 73, not only the abrasive having the grain size larger than the maximal grain size (for example, 100 μm) of the reusable abrasive, but also many cutting wastes produced in cutting of the workpiece 5 are sedimented and deposited. Since the cutting wastes often have a grain size larger than the grain size of the reusable abrasive, they are sorted by the first sorting member 73, and deposited on the relevant bottom area. Such abrasive or cutting wastes having the grain size larger than the maximal grain size are discharged from the second discharge port 93 provided in a side face of the housing 71 positioned in the relevant bottom area, and transported to the abrasive recovery filter 101 (refer to FIG. 1) via the pipe line 64. Since such abrasive or cutting wastes having the grain size larger than the maximal grain size may cause clogging of the discharge ditch or the like, they can not be drained as it is, therefore they are recovered by the abrasive recovery filter 101 and then disposed.

On the bottom area at the side near the flow outlet 92 compared with the second sorting member 74, abrasive having a grain size smaller than the minimal grain size of the reusable abrasive (for example, smaller than 25 μm) is sedimented and deposited, which further has a grain size causing dogging of the discharge ditch (for example, 10 μm to 25 μm) if the abrasive is discharged as it is. The abrasive is discharged from the third discharge port 95 provided in a side face of the housing 71 positioned in the relevant bottom area, and transported to the abrasive recovery filter 102 (refer to FIG. 1) via the pipe line 65. Since such abrasive having the grain size of 10 μm to 25 μm may cause dogging of the discharge ditch or the like, it cannot be drained as it is, therefore it is recovered by the abrasive recovery filter 102 and then disposed. While the abrasive discharged from the second discharge port 93 has not any possibility of being reused, since the abrasive discharged from the third discharge port 95 has a possibility of being reused in some other application, desirably, it is recovered separately from the abrasive discharged from the second discharge port 93.

Hereinbefore, detailed description has been made on the water jet cutting machine 1 according to the embodiment, particularly on the abrasive sorting tank 70 of the abrasive recovery unit 60. In the abrasive recovery unit 60 according to the embodiment, the abrasive mixture water is horizontally flown, and the reusable abrasive is sorted and recovered by using difference in sedimentation rate of abrasive depending on grain size without using the abrasive recovery filter 167 (refer to FIG. 4) like the abrasive recovery unit 160. Therefore, essentially, the abrasive recovery unit 60 can be continuously used for a long time without needing maintenance of the unit, consequently convenience of an operator can be improved.

Moreover, in such a sorting/recovery method by using difference in sedimentation rate of abrasive, compared with the case of using the abrasive recovery filter 167, abrasive is accurately sorted for each grain size, consequently uniform abrasive is easily obtained. Therefore, the relevant uniform abrasive is circularly used within the water jet cutting machine 1, thereby cutting quality of the workpiece 5 can be improved.

Hereinbefore, while the preferred embodiment and examples of the invention have been described with reference to accompanied drawings, the invention is not limited to such embodiment and examples. It will be appreciated that various alterations or modifications can be conceived by those skilled in the art within a category of technical ideas according to claims, and it is obviously understood that they also belong to a technical scope of the invention.

The workpiece 5 may include various semiconductor wafers, or semiconductor substrates such as a packaged substrate such as a CSP substrate, GPS substrate, or BGA substrate. Alternatively, the workpiece may include a sapphire substrate, a glass material, a ceramic material, a metal material, a synthetic resin material such as plastic, or an electronic material substrate for forming a magnetic head, laser diode head or the like. A shape of the workpiece 5 may be any optional shape such as an approximately rectangular shape or an approximately disk shape.

While an example of using the water jet cutting machine 1 as the abrasive water jet cutting machine was described in the embodiment, the invention is not limited to such an example. The abrasive water jet cutting machine can be variously altered in design if the machine has a high-pressure liquid jetting unit for jetting a high-pressure liquid, and can perform the cutting process of workpiece by jetting the high-pressure liquid. For example, the liquid to be jetted and retained is not limited to the example of water, and may be any other liquid such as alcohol or oil, or may be any of liquids in which various chemical substances are dissolved in various solvents.

INDUSTRIAL APPLICABILITY

The embodiment of the invention can be used for an abrasive water jet cutting machine for cutting workpiece by jetting a high-pressure liquid mixed with abrasive. 

1. An abrasive water jet cutting machine comprising: an abrasive-mixture-liquid retention tank for retaining an abrasive mixture liquid in which an abrasive and a liquid are mixed, a high-pressure liquid supply unit for feeding out the abrasive mixture liquid retained in the abrasive-mixture-liquid retention tank at high pressure by supplying a high-pressure liquid to the abrasive-mixture-liquid retention tank, a jet nozzle for jetting the high-pressure abrasive mixture liquid, which is fed out from the abrasive-mixture-liquid retention tank, to workpiece, a catch tank for receiving the high-pressure abrasive mixture liquid jetted from the jet nozzle, and an abrasive recovery unit that recovers abrasive having grain size in a reusable predetermined range from the abrasive mixture liquid transported from the catch tank, and transports abrasive mixture liquid including recovered abrasive into the abrasive-mixture-liquid retention tank, thereby cutting the workpiece by the high-pressure abrasive mixture liquid jetted from the jet nozzle; wherein the abrasive recovery unit has an abrasive sorting tank that flows the abrasive mixture liquid transported from the catch tank in an approximately horizontal direction, and sorts abrasive depending on grain size of the abrasive by using difference in sedimentation rate caused by grain size of the abrasive, and recover the reusable abrasive having the grain size in the predetermined range; the abrasive sorting tank has a flow inlet provided on an upper portion at one end side, a flow outlet provided on an upper portion at the other end side, a first sorting member as a partition member that is set at a side of the flow inlet in a bottom and divides the bottom, a second sorting member as a partition member that is set at a side of the flow outlet in the bottom and divides the bottom, and a first discharge port set between the first and second sorting members; and when the abrasive mixture liquid transported from the catch tank flows in the approximately horizontal direction from the flow inlet to the flow outlet, the abrasive sorting tank sediments abrasive having a grain size larger than a maximum of the reusable predetermined range included in the relevant abrasive mixture liquid in a side near the flow inlet side compared with the first sorting member, sediments abrasive having a grain size in the reusable predetermined range between the first and second sorting members, and sediments abrasive having a grain size smaller than a minimum of the reusable predetermined range in a side near the flow outlet side compared with the second sorting member, and discharges the abrasive having the grain size in the reusable predetermined range from the first discharge port and recover it.
 2. The abrasive water jet cutting machine according to claim 1, wherein height of the first and second sorting members may be changed.
 3. The abrasive water jet cutting machine according to claim 1, wherein the abrasive sorting tank further has a second discharge port set at a side near the flow inlet compared with the first sorting member in the bottom, and a third discharge port set at a side near the flow outlet compared with the second sorting member in the bottom, so that the abrasive having the grain size larger than the maximum of the reusable predetermined range is discharged from the second discharge port, and the abrasive having the grain size smaller than the minimum of the reusable predetermined range is discharged from the third discharge port.
 4. The abrasive water jet cutting machine according to claim 2, wherein the abrasive sorting tank further has a second discharge port set at a side near the flow inlet compared with the first sorting member in the bottom, and a third discharge port set at a side near the flow outlet compared with the second sorting member in the bottom, so that the abrasive having the grain size larger than the maximum of the reusable predetermined range is discharged from the second discharge port, and the abrasive having the grain size smaller than the minimum of the reusable predetermined range is discharged from the third discharge port. 